Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for LRA real time impedance tracking and BEMF extraction
Description of the Related Art
Linear Resonant Actuators (LRA) are very similar to mass loaded spring systems. LRA actuators can be modeled as Series RL with a BEMF voltage element, which is calculated based on mechanical properties of the LRA. For optimum efficiency, they are driven at the resonance frequency.
Estimating LRA actuator health, aging and failures before they occur can have substantial benefits for actuator manufacturers and end product manufacturers. Such estimation reduces failures on the field and facilitates the problem diagnostic process. LRA real-time impedance tracking algorithm can enable technologies such as actuator health monitoring, aging estimation, actuator temperature estimation, and the likes.
For LRA drivers, the BEMF voltage is sensed directly going to a high-impedance mode. In such architectures, BEMF sampling requires a halt in driving the signal, which lowers the efficiency/headroom at which the driver can work resulting in less acceleration. FIG. 1 is an embodiment of a sinusoidal BEMF wave superimposed on a driver output as implemented in the prior art. As shown in FIG. 1, the current architecture does not produce a square wave, since it cannot continuously drive the LRA.
The BEMF can also be extracted by measuring the load current if the LRA's impedance is known. Therefore, there is a need for a method and/or apparatus for LRA real time impedance tracking and BEMF extraction.